A bicycle display device is configured to accurately verify an amount of adjustment occurring when performing a fine adjustment of a transmission position of a transmission device. The bicycle display device is mounted on a bicycle, and includes a mounting part and a display element. The mounting part is attachable to a brake bracket of the bicycle. The display element is supported by the mounting part, and is configured and arranged to display a fine adjustment display screen for indicating the amount of adjustment when adjusting the transmission position of a transmission device such as a rear derailleur.